1. Field of the Invention
The present invention relates to a toner for electrophotography, used for developing an electrostatic latent image formed with a developing agent in an electrostatic photography process and the like, and to an image-forming method using the toner for electrophotography, an image-forming apparatus and a toner cartridge.
2. Description of the Related Art
Many electrophotographic methods are known, such as those disclosed in U.S. Pat. No. 2,297,691, Japanese Patent Application Publication (JP-B) No. 42-23910 and the like. Electrophotographic methods generally includes basic steps such as exposure, wherein an electrically latent image is formed onto a surface layer of photoreceptor that utilizes a photoconductive substance by various means; developing the image by using a toner; transferring the toner to a recording material such as paper; fusing the toner image on the recording material by heat, pressure, heat pressure or solvent vapor or the like; removing the residual toner from the surface layer of photoreceptor and the like. Recently, a demand has grown for low cost and small size copying machines and printers utilizing electrophotographic methods. In the process of designing such copying machines or printers, it is important to contain the amount of power required to fuse a toner, and also to simplify the method of fusing. The method most generally used at present is that of fusing using a heat roll as a means for melt-fusing a toner on a paper. In order to prevent melt-adhesion of a toner during heat-fusing of the toner, a heat roll has been used in which the roll surface layer is coated with a material having low surface energy, such as a fluorine resin, and materials to capable of being used for the roll surface have accordingly been limited. Furthermore, since, during heating of the fusing roll, heat conduction is sometimes impeded in the fluorine resin, for the purpose of obtaining effective heat conduction, the thickness of the fluorine resin on the surface layer of the fusing roll has been limited. Moreover, the resin can be abraded or damaged by repetitive use, and wettability on the surface of the fusing roll cannot be maintained over a long time period. Therefore, there has been a demand for the development of a toner that does not require any coating on the surface of a fusing roll, combined with a material having low surface energy such as a fluorine resin.
On the other hand, a pressure-fusing method using a metal roll is known (Japanese Patent Application Laid-Open (JP-A) No. 51-36947). However, this pressure-fusing method entails a problem, insofar that since the image is pressed by pressure the fusing property of the fusing image is weak, e.g., images have easily peeled off as a result of external forces as small as a pressure exerted by a ballpoint pen. Furthermore, in order to improve fusing property in the pressure-fusing method, attempts have been made to prepare a microcapsule toner having a microphase separation structure composed of continuous phases of resin and a solvent having high a boiling point (JP-A No. 6-19182). However, since a solvent component is used in this method, the method has entailed problems in therms of storage stability and the blocking property of the fused image.
Furthermore, two oil-less fusing methods that do not require any feeding of oil to a heat roll are known, one, a method of adding to a toner a release agent such as a wax (JP-A No. 61-62045), and the other, a method for defining the storage elasticity of a resin, by noting the adhesive force to a recording medium during melt-fusing of a toner and the aggregation force of the melt toner (JP-A No. 1-303447). Furthermore, a method for controlling the above-mentioned elasticity by internal addition of microparticles (JP-A No. 8-220800), a method for defining the elasticity in a toner in which microparticles have been internally added (JP-A No.2001-305794) and the like are known. However, in each of these methods, in order to obtain a releasing property a heat-fusing roll is required having the kind of low surface energy described above.